Atomic Bombs

The first a-bomb called (Little Boy) was a uranium gun-type atomic bomb.

The second a-bomb called (Fat Man) was a plutonium implosion-type bomb.

Proof of this can be seen by studying the actions of the Japanese Army AFTER we dropped two bombs. They insisted the war continued, in fact they tried to kill anyone that would relay the Emperor's surrender message. (Which was on a record.)

Why were they unimpressed by the A-Bombs? The fire bombing of Tokyo destroyed more homes, and killed more people than the A-Bomb. So the A-Bomb did not impress the Army. For some reason it did impress the Emperor.

Japan in the summer of 1945 suffered from three major problems in terms of food and war material production:

1. The US submarine force had all but annihilated the Japanese merchant marine, with almost all ocean-capable ships sunk, and very few of the coastal shipping vessels still surviving. Japan had no way to ship via sea any amounts of food or raw materials from their production/growing sites to where they would be consumed.
2. Japan had very little in the way of railroad infrastructure, mostly due to the extremely mountainous terrain of much of the Home Islands. The modest amounts of railroads that had been built were in very limited areas. This made it rather simple for the US Strategic Bombing campaign to destroy it all. By mid-1945, the Japanese railroad infrastructure was in the same shape as the shipping industry - rapidly approaching complete destruction.
3. A rice blight was raging throughout the islands, which, combined with the loss of much of the existing agricultural workforce to bombing and war death, meant that a very serious lack of rice was in the offering. Japan was looking at at rice famine in the winter of 1945.

The three factors above combined to mean that very little rice was going to be harvested, and what rice there was could not be distributed to where it was needed (primarily the cities). This meant that a massive famine was rapidly approaching. In fact, even after the August surrender and the occupation of Japan by the Allies (and, massive importation of food, primarily from the US), Japan suffered one of its more severe famines during the winter of 1945-46.

It's not unreasonable to assume that 80-90% of the total Japanese population would have gone hungry during the winter of 1945-46 if they had not surrendered. A 20-25% death toll from starvation was well within possibilities. Japanese culture was built on the implied social contract that had the nobility and ruling classes exchange protection and social niceties for the guaranty that everyone would be at least minimally fed. Once this social compact was broken, an almost certain internal uprising would have occurred, resulting in a likely Civil War.

Thus, the Japanese would almost certainly have surrendered sometime in very late 1945, or, more likely early/mid-1946. However, the country would have been in anarchy, and, even more than in August 1945, completely (materially and culturally) destroyed. The human costs of such a scenario make the atomic bombings look like drops in a bucket. Estimations of starvation deaths for a Japan determined to hold out into 1946 are in the 10s of millions - thus, there's a strong possibility that Japan would have had more deaths than even the 26 million of the USSR, from a country with less than one-third the population. That is, over two orders of magnitude more deaths than the atomic bombings.

We did not specifically choose either Nagasaki nor Hiroshima for the atomic bombing. We chose a target list of 6 cities, with the primary criteria being they had not already been significantly bombed conventionally. This criteria was used both to help the Japanese quickly see the destructiveness of this new bomb and to help the US military evaluate bomb effects after the Japanese surrender. On the original list Kyoto was included, but Stimson demanded it be removed due to its cultural significance so Nagasaki was selected to replace Kyoto.

Actual target selections for the attacks were made a couple days before by the field commanders from this list, a primary and a secondary target for each attack. IIRC the primary and secondary target cities for each attack were:

1. August 6, 1945 - primary Hiroshima - secondary Kokura
2. August 9, 1945 - primary Kokura - secondary Nagasaki

The bomb was actually dropped on Nagasaki instead of Kokura on the 9th due to a combination of bad weather and some mechanical problems preventing access to fuel in one tank of the bomber on that mission (Bocks Car). So in a way you could say that the weather choose Nagasaki to atomic bomb as much as the US did.

Had it been necessary to continue the atomic bombing, the Manhattan Project factories were scheduled and ready to produce a total of 23 bombs for delivery on Japanese cities (not just the 2 used) before the end of 1945.

On August 2, 1939, just before the beginning of World War II, Albert Einstein wrote to then President Franklin D. Roosevelt. Einstein and several other scientists told Roosevelt of efforts in Nazi Germany to purify uranium-235, which could be used to build an atomic bomb. It was shortly thereafter that the United States Government began the serious undertaking known then only as "The Manhattan Project." Simply put, the Manhattan Project was committed to expediting research that would produce a viable atomic bomb.

A massive enrichment laboratory/plant was constructed at Oak Ridge, Tennessee. Harold Urey and his colleagues at Columbia University devised an extraction system that worked on the principle of gaseous diffusion, and Ernest Lawrence (inventor of the Cyclotron) at the University of California in Berkeley implemented a process involving magnetic separation of the two isotopes.

Next, a gas centrifuge was used to further separate the lighter U-235 from the heavier, non-fissionable U-238. Once all of these procedures had been completed, all that needed to be done was to put to the test the entire concept behind atomic fission ("splitting the atom," in layman's terms).

At 5:29:45 (Mountain War Time) on July 16, 1945, in a white blaze that stretched from the basin of the Jemez Mountains in northern New Mexico to the still-dark skies, "The Gadget" ushered in the Atomic Age. The light of the explosion then turned orange as the atomic fireball began shooting upwards at 360 feet per second, reddening and pulsing as it cooled. The characteristic mushroom cloud of radioactive vapor materialized at 30,000 feet. Beneath the cloud, all that remained of the soil at the blast site were fragments of jade green radioactive glass created by the heat of the reaction.

The brilliant light from the detonation pierced the early morning skies with such intensity that residents from a faraway neighboring community would swear that the sun came up twice that day. Even more astonishing is that a blind girl saw the flash 120 miles away.

Upon witnessing the explosion, its creators had mixed reactions. Isidor Rabi felt that the equilibrium in nature had been upset as if humankind had become a threat to the world it inhabited. Robert Oppenheimer, though ecstatic about the success of the project, quoted a remembered fragment from the Bhagavad Gita. "I am become Death," he said, "the destroyer of worlds." Ken Bainbridge, the test director, told Oppenheimer, "Now we're all sons of bitches."

After viewing the results several participants signed petitions against loosing the monster they had created, but their protests fell on deaf ears. The Jornada del Muerto of New Mexico would not be the last site on planet Earth to experience an atomic explosion.

Truman did not just "drop the atomic bomb", he had the Army, Navy, and Marines simultaneously preparing every single option available for destroying Japan's military ability to continue the war. Some of these were already in process, some of them were on the verge of being used, some of them would take significant time to prepare before they could be used.

1. The Army Air Forces were already carrying out multiple nightly 1000 plane firebombing raids, each of these firebombing raids did as much damage and killed as many people as one of the atomic bombs did.
2. The Army Corp. of Engineers Manhattan Project had plans and facilities to produce 23 atomic bombs by the end of 1945 (and many more in 1946, 1947, etc. if necessary). The first 2 of these became available in August and were used on August 6 and August 9. A 3rd had been manufactured before the Japanese surrender and could have been used sometime in late August.
3. The US and USSR had agreed that the Soviets would declare war on Japan in the middle of August and attack both Manchuria and the far northern islands of Japan. The Soviets actually accelerated this after the atomic bombing.
4. The Navy, Marines, and Army were planning and making preparations for a massive D-day invasion (bigger than the 1944 Normandy D-day invasion) of southern Japan in late October or early November of 1945.
5. Large stockpiles of chemical weapons (e.g. nerve gas, mustard gas) were being prepared for use during the invasions of Japan.
6. The Navy, Marines, and Army were planning and making preparations for a massive D-day invasion (bigger than the 1944 Normandy D-day invasion) of northern Japan in the spring of 1946.

The reason any and all of these options were being used or being prepared to be used was simple: it was believed that Japan would "fight to the last man" and unless their military ability to continue the war was completely destroyed the war in the pacific was not going to end. It seemed likely that this might require a 90% or larger fatality rate of the Japanese and the US was both willing and prepared to do that if it was actually necessary! Every single option and means to do this was in use by Truman!

The 1st atomic bomb codenamed the "Gadget" was exploded on July 16, 1945 SW of Socorro, New Mexico. It was an implosion type bomb using Plutonium 239. It was a test of nuclear bombs codenamed the "Trinity" test.

The 2nd atomic bomb codenamed "Little Boy" was exploded on August 6th, 1945 over the city of Hiroshima in Japan. It was a gun type bomb using Uranium 235. It was the 1st bomb dropped in anger.

The 3rd atomic bomb codenamed "Fat Man" was exploded on August 9th, 1945 over the city of Nagasaki. Like the Gadget it was an implosion type bomb using Plutonium core.